Not applicable.
1. Technical Field
This is a Divisional of U S. patent application Ser. 09/253,308 filed Feb. 19, 1999, now U.S. Pat. No. 6,290,438, of the same inventor.
The invention relates to a reaming tool and a process for its production.
Reaming tools are used for the fine machining of boreholes and therefore require a precise arrangement and design of chip removal elements and guide elements. In particular, a high degree of dimensional accuracy is desired.
2. Background Art
Reaming tools have already been known in which the chip removal elements or guide elements are set into a base body, for example by brazing or by adhesion. It has become known from German Patent DE 196 21 813 A1 to form a corresponding seating for the positioning of guide strips in order to make the seating of the inset chip removal elements and guide elements precise, so that these can be exactly positioned with respect to the base body. A considerable improvement was attained by this design.
However, the increasing quality requirements require a further improvement in the quality of reaming tools: for example, in the bonding between the chip removal elements and guide elements and the base body, and also with regard to the dimensional stability and to their production, in particular to cost-favorable production with consistent high quality.
For example, it is known, for milling tools or shaft milling tools, to use blanks with groove-shaped recesses which run along the envelope surface, and into which very hard cutting materials, such as, for example, PCD or CBN material, are sintered. Such blanks are processed by a spark erosion grinding process in order to produce shaft milling tools. Multi-cutter millers are concerned here for high performance machining.
The invention has as its object to provide a reaming tool and a process for its production, which tool can be produced cost-effectively, satisfies the high quality requirements, is flexible in design and construction, and reliably takes up the forces acting on it.
This object is attained according to the invention by a reaming tool with a shaft and a head on which at least one cutter is provided. The head is produced from a blank that comprises a base body of a base material with an envelope surface with at least one rectilinear or helical groove-shaped recess running around it, into which at least one high hardness cutting material is sintered. The high hardness cutting material comprises at least one cutter having cutting surfaces formed by the introduction of a chip groove by a grinding wheel into the base body, and movement of the grinding wheel toward the high hardness cutting material.
By the use of a blank which has on its envelope surface substantially rectilinear or helical groove-shaped recesses, into which high hardness cutting materials are sintered, a cost-favorable production and manufacture of a reaming tool can be provided. An expensive preparation for the introduction of seatings for chip removal elements and/or guide elements is dispensed with by the hard cutting material already present in the blank, since the sintered-in hard material layers can be used as chip removal strips and/or guide strips specifically according to the application, and can be machined to dimension. Furthermore, this advantageous embodiment makes it possible for the shaft of the reaming tool to be made of a cost-favorable material which can be positively connected, but however preferably non-positively connected, to the shaped head.
The use of blanks with high hardness cutting materials provided in groove-shaped recesses and running around the envelope surface at first appears to be erroneous. End milling tools in which the use of blanks is known are used for machining workpieces in the X-Y plane. The end miller then has, along its rotation axis, peripheral cutters constituted as a main cutter and coming into use in milling machining. The cutters arranged to the end of the milling tool play no, or only a very subsidiary, part. Furthermore, end millers operate at relatively high cutting speeds and depths of cut, so that quite other forces act on a head of an end miller.
In reaming tools, on the contrary, the machining and the chip formation are determined by completely different parameters and dimensions. In milling machining, the borehole is machined exclusively in the Z-direction, and in contrast machining in the X- and Y-directions is neither provided nor possible. Furthermore, at least one main cutter is arranged to the end of a reaming tool, and in contrast at least one auxiliary cutter is provided along the rotation axis and has essentially the task of guiding. The use of such blanks with high hardness cutting materials arranged in grooves and extending substantially coaxial to the rotation axis therefore would appear to be unsuitable, particularly when costs are taken into account. The same holds for the use of reaming tools because of the forces, parameters and requirements which deviate from milling technology, and which at first sight make the use appear to be erroneous to form the reaming tool by means of a blank which has on its envelope surface substantially rectilinear or helical groove-shaped recesses, into which high hardness cutting material is sintered.
However, by the constitution of a reaming tool according to the invention, the constitution of a reaming tool with twisted chip formation elements and/or guide elements is attained, which heretofore has not been possible. This can be made possible, for example, for a multi-cutter reamer which has cutters of high hardness cutting materials. A single cutter reaming tool with guide strips can likewise be provided, in which both the chip removal element and also the guide elements, or one of the two, is twisted. A considerable improvement can thereby be attained as regards the processing quality, the speed, and also the life of the tool. This is based on the fact that the chip removal elements and guide elements are sintered into the base body of the shaped head, so that a material joint of higher quality than the usual brazed joint can thereby result. Furthermore, the labor-consuming brazed joints and the production of seatings for plates or guide strips are dispensed with, together with the associated risks of defective brazed places which can arise because of negligent cleaning of the contact surfaces.
According to a further embodiment of the invention a PCD material is used as the high hardness cutting materials. This can be used specifically for the application, corresponding to the material to be machined, such as for example the machining of nonferrous metals.
According to a further embodiment of the invention, a CBN material is used as the high hardness cutting material. This suitable material can be used corresponding to the further materials to be machined.
According to a further embodiment of the invention, the high hardness cutting materials are constituted as the chip removal element and/or guide element. Both elements have, due to the sintering process, a chemical connection to the base body of the blank, and because of the diffusion process which then takes place and which can, for example, give rise to a cobalt or nickel compound, has a substantially higher strength than a brazed or adhesive joint.
According to a further embodiment of the invention, the chip removal elements and the guide elements can be constituted as either right-twisted or left-twisted. The corresponding design of the reaming tool can thus be made possible according to the application.
According to a further embodiment of the invention, chip grooves can be made in the blank by grinding. Depending on the respective application, the high hardness cutting materials are ground to dimension for one or more cutters and guide strips, or solely for chip removal elements or guide elements. In both of the last alternatives, the guide elements or cutter elements can be supplemented by corresponding inserted elements.
According to a further embodiment of the invention, the length, or else only the forward portion, of the blank can be determined by the length of the auxiliary cutter, or by the length of the guide strip. It can then be provided that one or more blanks are arrayed, corresponding to the application: for example, in the case of stepped boreholes.
The object of the production of a reaming tool is attained by a process for production of a reaming tool with a shaft and a head with at least one cutter comprising positively connecting a shaft to a blank that has at least one groove-shaped recess arranged on its envelope surface into which high hardness cutting materials are sintered, bringing the external diameter of the blank to the exact dimension of the flight circle diameter of the at least one cutter, producing at least one chip groove in the blank, bringing to said exact dimension the at least one cutter, producing at least one chip groove in the blank with a grinding wheel, and bringing the at least one cutter to said dimension.
According to a further embodiment of the invention the grinding wheel is moved toward the recess receiving the high hardness cutting material, and a chip surface of the at least one cutter is brought to said dimension.
A reaming tool can be constituted according to the invention, which is substantially determined by the reduction of the individual working steps. By the employment of a blank with high hardness cutting materials provided in groove-shaped recesses on a shaft, the costly preparation of a base body in order to seat chip removal elements and guide elements, and the subsequent brazing of these, can be dispensed with. By the grinding of the blank to dimension, a rapid shaping of a reaming tool can be given by means of a single clamping. At the same time, a high constancy of dimensions can be given, since repeated resetting of the workpiece is not required. A reaming tool can thus be produced by the process according to the invention, in which both the at least one chip removal element and also the at least one guide element are constituted by the high hardness cutting material arranged on the blank.
Further alternative processes, of equal value, for the production of such reaming tools are given herein. Thereby, according to the application, chip removal elements or guide elements which are different from the chip removal elements or the guide elements arranged on the blank can be used, in order to fulfill the specific requirements. Furthermore, a reaming tool can be produced by an alternative according to the invention which, as a multi-cutter tool, consists exclusively of cutters which consist of the high hardness cutting materials provided on the blank.